Tobacco curing

ABSTRACT

Tobacco curing system in which a spirally-wound reel containing tobacco leaves is placed in a chamber having flexible walls. The chamber is then evacuated to cause the ambient atmosphere to urge the flexible walls inwardly and exert pressure on the tobacco and effect a seal therewith. Preheated air is passed through the tobacco while subatmospheric pressure is maintained in the chamber, to cure the tobacco.

United States Patent [1 1 Clark [111 3,773,054 1 Nov. 20, 1973 TOBACCO CURING [76] Inventor: Emmett T. Clark, 513 N. Guthrie Ave.. Durham. N.C. 27703 [22] Filed: Apr. 7, 1971 [21] Appl. No.: 131,895

[52] US. Cl. 131/133 A, 34/92, 131/140 A [51] Int. Cl A24b 01/02 [58] Field of Search 131/140 A, 140 R,

131/133 A, 134, 149, 140 P; 34/92, 15; 263/19 D; 214/55 [56] References Cited UNITED STATES PATENTS 2,124,012 7/1938 Smith 131/140 P 3,280,473 10/1966 Sullivan 34/92 2,929,154 3/1960 Finnegan 34/92 3,225,456 12/1965 Touton 131/134 X FOREIGN PATENTS OR APPLICATIONS 696,551 9/1953 Great Britain 131/140 P OTHER PUBLICATIONS Yoder; E. E., Field-Curing Burley Tobacco Under Plastic, Tobacco Abstracts Vol. 13, N0. 5, May 1969, pg. 547 Item 1378.

Primary Examiner-Robert W. Michell Assistant ExaminerJohn F. Pitrelli Attorney-Shanley & ONeil [5 7 ABSTRACT Tobacco curing system in which a spirally-wound reel containing tobacco leaves is placed in a chamber having flexible walls. The chamber is then evacuated to cause the ambient atmosphere to urge the flexible walls inwardly and exert pressure on the tobacco and effect a seal therewith. Preheated air is passed through the tobacco while subatmospheric pressure is maintained in the chamber, to cure the tobacco.

3 Claims, 3 Drawing Figures VACUUM PUMP 68 Patented Nov. 20, 1973 3,773,054

2 Sheets-Sheet l INVENTOR EMMETT T. CLARK ATTORNEYS Patented Nov. 20, 1973 2 Sheets-Sheet 2 FIG 2 e O O O O O 0 TOBACCO CURING BACKGROUND OF THE INVENTION It has been estimated that about 90 percent of present-day tobacco curing is done in large stick-type barns. The tobacco leaves are tied in bundles of a few leaves each, and the bundles are tied at spaced locations along an elongated stick. A multiplicity of sticks is hung in tiers in the curing barn, and one or more heaters are placed on the floor below. Air preheated to temperatures up to 180 F and higher convectively rises through the tiered bundles to vents at the top of the barn and effects curing of the tobacco.

This procedure is highly disadvantageous, inter alia, because of the great amount of hand labor which is required. The tobacco leaves must be tied in bundles and the bundles tied on sticks, and the sticks then hung in the barn. After the tobacco is cured, the sticks must be taken down and the bundles untied and removed from the sticks. There is a growing shortage of agricultural labor in the tobacco-producing regions, and so the necessary labor for all the required manual handling of the tobacco is becoming increasingly more difficult to locate, and the costs of the labor are steadily rising. The large amount of handling involved in stick-bam curing is also disadvantageous because tobacco can be damaged by careless or rough handling. Also, the heating of the air which is to flow through and around the tobacco bundles is something of a delicate operation; too much heat can result in scalding damage to the tobacco.

The only other tobacco curing procedure which is employed to any great extent is the bulk curing system. In this system, the tobacco leaves are tightly packed in steel racks and the racks are placed tightly beside one another in a large barn. Heated air is forced into the bottom of the barn by high-pressure fans, and the fans force the air up through the tobacco in the racks and out through the top of the barn.

The bulk curing barns save some labor because it is easier to pack the tobacco in the racks than to tie bundles of leaves on sticks. However, bulk curing is disadvantageous because it is difficult to pack the tobacco in the racks to a uniform degree of tightness so that the proper amount of air flows through all the tobacco. If, as usually occurs, some racks are packed more loosely than others, more air passes through the losse racks than through the tighter racks, and the cure is nonuniform. Scalding as a result of excessive heating is also a problem in bulk curing.

Main objects of the invention are the provision of im proved tobacco-curing systems which are more economical and efficient than those of the prior art, which require a minimum amount of hand labor, and in which uniform curing is effected with minimization of scalding damage.

Other objects and advantages of the invention will appear from the following detailed description which, when considered in connection with the accompanying drawings, discloses a preferred embodiment of the invention for purposes of illustration only.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side cross-sectional view schematically illustrating a tobacco-curing system embodying principles of the invention.

FIG. 2 is a cross-sectional view on line 2-2 of FIG. 1.

FIG. 3 illustrates the manner in which the tobacco leaves are supported in the system of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, tobacco curing apparatus 10 includes a chamber 12 having a bottom end portion 14, a top end portion 16, and a generally circular cross-section (see also FIG. 2). An air inlet 18 is provided at bottom end 14, and an air outlet 20 is provided at top end 16. Air flows through chamber 12 from bottom to top as indicated by directional arrows.

Tobacco leaves 22 to be cured are preferably supported stems-up in chamber 12 by an arrangement including a reel 24 mounted on a base assembly 26. Where desired, the leaves may be in stems-down position or randomly arranged. Tobacco leaves 22 are sewn to a continuous web 28 (see also FIG. 3) of cheesecloth or other porous fabric and the web is spirally wrapped upon reel 24 with tobacco leaves 22 held between the spiral convolutions of the web. FIG. 3 depicts a segment of web 28 as it appears when unwound from reel 24. The reel itself includes a hollow central hub 30 (FIG. 1) and upper and lower flanges 32, 34 which extend radially outwardly from opposite axial ends of hub 30. Each flange is foraminous (see also FIG. 2), having a multiplicity of airflow passages or perforations 36 across the breadth of the flange.

Reel 24 of spirally-wound tobacco leaves can be produced in any suitable way, but is advantageously made in accordance with the teachings of my copending patent application Ser. No. 814,963, filed Apr. 10, I969, now Pat. No. 3,606,723, which discloses tobaccoharvesting systems of the same general type as in my prior US. Pat. No. 3,470,882. In such systems, a tobacco-harvesting machine moves through a tobacco field, the leaves are picked, placed on a continuous web and sewn to the web which is spirally wrapped as the harvesting machine moves through the field.

Irrespective of how the reel of tobacco is produced, airflow through hollow hub 30 of the reel is prevented by plugs 38 which are placed in the ends of the hub.

Base assembly 26, which supports reel 24, is hollow and includes a base box 40, a narrow neck 42, and a generally frustoconical, plate metal support member 44. Frustoconical support 44 diverges upwardly and serves to direct airflow radially outwardly across lower foraminous flange 34, so that air can flow through the tobacco in the outer peripheral portions of the reel. The reel periphery rests on circular rim 46 of frustoconical support 44.

Air inlet 18 is in the form of a tube which communicates between the ambient atmosphere and the hollow interior of base box 40. An adjustable control valve 48 is provided in inlet tube 18 to vary the amount of air which flows into base assembly 26, and thereby control the amount of air flowing through the tobacco. The incoming air passes in heat exchange relationship with an electric heater 50 in base box 40, so that the air is heated to an elevated temperature before flowing through the tobacco as described in more detail hereinafter. Heater 50 can be adjusted to vary the preheat temperature of the incoming air.

A generally frustoconical sheet metal member 52 is provided above reel 24. Frustoconical member 52 converges upwardly, and directs airflow from perforations 36 in upper reel flange 32 to air outlet 20 which is in the form of a tube at the apex portion of a frustoconical member 52. The circular bottom rim of upper frustoconical member 52 rests upon the outer periphery of top reel flange 32.

A vacuum conduit 54 is slipped over the upper end of air outlet tube 20, and an O-ring 56 efiects an airtight seal at the joint. Vacuum conduit 54 has flexible joints 58, 60 which facilitate positioning of the end of vacuum conduit 54 over outlet tube 20, and removal therefrom. Vacuum conduit 54 is supported by a rope 62 from a projecting arm 64 of a ground-mounted support frame 66.

Vacuum conduit 54 communicates air outlet 20 with a vacuum pump 68 which together with air inlet 18 and outlet 20, form air-circulating structure for evacuating chamber 12 to subatmospheric pressure and for flowing air through the tobacco in the chamber while maintaining subatmospheric pressure in the chamber. Preferably, the chamber is evacuated to and maintained at a vacuum of at least about 0.5 inches Hg, i.e., about 0.5 inch Hg below atmospheric pressure, although any subatmospheric pressure which will hold the shrinking tobacco leaves as described below will suffice.

An air-impermeable, flexible, tubular film 70 has an upper end portion which is releasably sealed to outlet tube 20 by an annular clamp 72. Film 70 extends downwardly from clamp 72, covering frustoconical member 52, spanning the vertical distance between reel flanges 32, 34, and extending inwardly under lower frustoconical member 44 to neck 42 where film 70 is releasably sealed by another annular clamp 74.

Flexible film 70 is preferably of plastic material, e.g., polyethylene about 4 mils in thickness. Film 70 provides for chamber 12 flexible wall portions 76 which span the gap between reel flanges 32, 34 around the circumference of the reel. Flexible walls 76 are positioned contiguous to the tobacco to be urged inwardly by the ambient atmosphere for exertion of pressure on the tobacco upon evacuation of the chamber to subatmospheric pressure. Tobacco contracts or shrinks as it cures, and thus provides additional space between web convolutions and between leaves in the reel for air to bypass the tobacco instead of flowing through the leaves. Exertion of pressure by the atmosphere against the tobacco uniformly all around the reel serves to compress the reel and thereby reduce the available bypass flow space and force the air to flow through the tobacco in the reel instead of around it through the shrinkage spaces. Further, flexible walls 76 are urged into sealing relationship with the outer periphery of the convoluted web, so as to force the air in chamber 12 to flow through perforations 36 and through the convolutions in the reel from bottom to top, instead of around the reel of tobacco. Still further, where the invention is carried out without sewing the tobacco to the web, the pressure exerted on the reel through the flexible walls serves to support the tobacco to retard the tendency for the tobacco to slip downwardly between wraps as the tobacco shrinks on curing. Moreover, flexible film '70 makes it possible to drastically reduce the cost of curing chambers or barns, and to rapidly assemble and disassemble the barn for insertion and extraction of tobacco reels.

A series of pleats 78 of excess material is provided in flexible film 70 to allow the film to be urged inwardly between reel flanges 32, 34 without tearing the flexible film. There is sufficient excess material provided in gathers or folds at the top and bottom of the film to permit the film to be slipped without tearing over the reel and frustoconical members from top to bottom.

in a specific example of operations in accordance with the invention, reel 24 of tobacco is placed on lower frustoconical member 44; upper frustoconical member 52 is then placed upon reel 24. Flexible tubular film is then slipped over the assembly from top to bottom, gathered at top and bottom, and secured by clamps 72, 74. The free end of vacuum conduit 54 is then manipulated into position and slipped over the open upper end of outlet tube 20.

Vacuum pump 68 is then started and chamber 12 is evacuated to a subatmospheric pressure of about 0.5 inch Hg vacuum. Upon evacuation, the ambient atmosphere urges flexible walls 76 inwardly against the periphery of the tobacco to form a seal and exert pressure on the tobacco. Under the influence of vacuum pump 68, air flows in through inlet tube 18. Control valve 48 is adjusted to provide a rate of airflow of about 10 cubic feet per minute. Heater 50 is left switched off for the time being, so the incoming air is not preheated but rather, remains at ambient temperature. Under the influence of the vacuum pump, the air flows from the bottom of chamber 12 through lower reel flange 34, upwardly through the tobacco leaves and upper reel flange 32 and out through outlet conduit 20 and vacuum conduit 54. The procedure is continued for 3 days, during which time the ambient temperature varies from about F to about F. At the end of that time, heater 50 is switched on and adjusted to preheat the incoming air to about F. At the end of 12 hours, the preheat temperature is increased to about F. At the end of 6 more hours, the preheat temperature is increased to about 1 30 F and left at that temperature for 24 hours to complete the cure. At the end of that time, the vacuum pump and heater are turned off and vacuum conduit 54 is removed from air outlet 20. Annular clamps 72, 74 are released, and flexible film 70 is slipped upwardly off reel 24 and frustoconical members 44, 52. Frustoconical member 52 is lifted from reel 24, and the reel is lifted from frustoconical member 44. Another reel of tobacco to be cured is placed on frustoconical member 44, and the process is re peated.

Tobacco curing systems according to the invention are highly advantageous. The reel-curing aspects eliminate the manual labor hitherto necessary for tying the tobacco leaves in bundles, tying the bundles on sticks, hanging the sticks in barns, taking down the sticks and untying the leaves. Yet, the problems of loose and tight packing associated with bulk curing are not presented in systems according to the invention, because airflow is uniform throughout the reel.

With vacuum curing, less heat is required. That is to say, the circulating air need not be heated to as high a temperature, or for as long a period of time, as in conventional curing procedures. Effective curing is possible at temperatures of below about F, preferably below about 130 F, in contrast with the temperatures of up to F and higher which are used in conventional curing systems. With less heat, there is less risk of scalding damage to the tobacco. In point of fact, solar heat alone can be employed to cure tobacco in accordance with the invention. In such case, the incoming air is used at ambient atmospheric temperature without preheating. Such temperatures usually vary from about 75 F to 95 F in the tobacco-growing regions at the curing season. However, the solar-heating procedure appears to be of less advantage than with preheating because of long curing times required.

Where desired, heat alone without vacuum can be used or vacuum alone without heat.

The circular tobacco-curing apparatus or barns provided by the invention are quite small and inexpensive; the large expensive curing barns hitherto employed are eliminated. And, with a circular cross-section for the curing barn, there are no corner pockets of stagnant airflow as are commonly associated with conventional polygonal structures.

The invention has been described with reference to a preferred embodiment which was set forth for purposes of illustration only and not for definition of the limits of the invention. It will be apparent that many variations of the time, temperature, pressure and airflow parameters of the process can be performed and yet still effect satisfactory curing of the tobacco. These and many other modifications of the preferred embodiment can be made, as those skilled in the art will readily perceive. Such modifications are within the scope of the appended claims, to which reference will be had for definition of the principles of the invention.

1 claim: 1. Tobacco curing apparatus, comprising means defining a chamber, support means for supporting tobacco to be cured in the chamber, the support means including a reel having foraminous flanges, an elongated web member spirally wrapped upon the reel for holding between convolutions tobacco to be cured, base means for supporting the reel in the chamber, air-circulating means for evacuating the chamber to subatmospheric pressure and for flowing air through the tobacco in the chamber while maintaining subatmospheric pressure in the chamber,

the chamber having flexible walls which are contiguous to the tobacco and which are movable inwardly by the ambient atmosphere for exertion of atmospheric pressure on the tobacco upon evacuation of the chamber to subatmospheric pressure,

the chamber having opposite end portions,

the air-circulating means including means defining an air inlet at one end portion of the chamber,

means defining an air outlet at the other end portion of the chamber, and

a vacuum pump communicating with the air outlet,

the flexible walls of the chamber being positioned relative to the tobacco so that when urged into contact with the tobacco by the atmosphere they force air flowing from the one end portion of the chamber to the other end portion of the chamber to flow through the tobacco instead of between the tobacco and the walls of the chamber.

2. The apparatus of claim 1; including means for directing the airflow through the foraminous flanges away from the air inlet and toward the air outlet.

3. Tobacco curing apparatus, comprising means defining a chamber,

support means for supporting tobacco to be cured in the chamber,

air-circulating means for flowing air through the tobacco in the chamber,

the support means including a reel having foraminous flanges,

an elongated web member spirally wrapped upon the reel for holding between convolutions tobacco to be cured, and

base means for supporting the reel in the chamber. 

1. Tobacco curing apparatus, comprising means defining a chamber, support means for supporting tobacco to be cured in the chamber, the support means including a reel having foraminous flanges, an elongated web member spirally wrapped upon the reel for holding between convolutions tobacco to be cured, base means for supporting the reel in the chamber, air-circulating means for evacuating the chamber to subatmospheric pressure and for flowing air through the tobacco in the chamber while maintaining subatmospheric pressure in the chamber, the chamber having flexible walls which are contiguous to the tobacco and which are movable inwardly by the ambient atmosphere for exertion of atmospheric pressure on the tobacco upon evacuation of the chamber to subatmospheric pressure, the chamber having opposite end portions, the air-circulating means including means defining an air inlet at one end portion of the chamber, means defining an air outlet at the other end portion of the chamber, and a vacuum pump communicating with the air outlet, the flexible walls of the chamber being positioned relative to the tobacco so that when urged into contact with the tobacco by the atmosphere they force air flowing from the one end portion of the chamber to the other end portion of the chamber to flow through the tobacco instead of between the tobacco and the walls of the chamber.
 2. The apparatus of claim 1; including means for directing the airflow through the foraminous flanges away from the air inlet and toward the air outlet.
 3. Tobacco curing apparatus, comprising means defining a chamber, support means for supporting tobacco to be cured in the chamber, air-circulating means for flowing air through the tobacco in the chamber, the support means including a reel having foraminous flanges, an elongated web member spirally wrapped upon the reel for holding between convolutions tobacco to be cured, and base means for supporting the reel in the chamber. 